FR2945753A1 - Installation for treating effluent and discharging treated effluent in soil, comprises filtration unit equipped with gravity filter bed, and basin for receiving filtered effluent partially buried in soil, where basin defines buffer zone - Google Patents

Abstract

The treatment installation (1) comprises a filtration unit (3) equipped with a gravity filter bed (5), and a basin (4) for receiving filtered effluent partially buried in the soil. The basin defines a buffer zone in which the filtered effluent is accumulated. A part of a peripheral wall (40) of the basin has through-holes made at different heights of the peripheral wall of the basin to allow the discharge of the treated effluent at different soil depths. The basin extends around the filter unit so that the buffer zone is provided between the inner and outer surfaces of the peripheral wall. The treatment installation (1) comprises a filtration unit (3) equipped with a gravity filter bed (5), and a basin (4) for receiving filtered effluent partially buried in the soil. The basin defines a buffer zone in which the filtered effluent is accumulated. A part of a peripheral wall (40) of the basin has through-holes made at different heights of the peripheral wall of the basin to allow the discharge of the treated effluent at different soil depths. The basin extends around the filter unit so that the buffer zone is provided between the inner surface of the peripheral wall of the basin and the outer surface of the peripheral wall of the filtration unit. The filtration unit is configured to allow discharge of the filtered effluent at its bottom portion, rests on the bottom wall of the basin so that the buffer zone affects a circular shape, and is formed as a container such as a tank of which the peripheral wall is cylindrical and houses the filter bed. The peripheral wall of the container has through holes on its entire periphery at different heights. The through holes are formed in the peripheral wall of the container of the filtration unit to a height of the filter bed. The filter bed is housed in a porous envelope partially filled with filtering elements and/or adsorbent materials. The part of the peripheral wall of the basin is surrounded by a layer of gravels through which the treated effluent is intended to be percolated, discharged from the buffer zone of the basin before infiltrating into the ground. The basin is further equipped with an overflow outlet connecting with a discharge pipe extending along horizontal infiltration trench made in the ground, and is perforated on a part of its length to distribute the overflow of recovered effluent along the infiltration trench. An independent claim is included for a treatment station comprising a finishing installation.

Description

The present invention generally relates to the treatment of effluent for the discharge of treated effluent into the soil.

The invention relates more particularly to an effluent treatment plant comprising a filtration unit equipped with a filter bed. The invention also relates to a treatment station comprising such a treatment plant.

Usually, for individual sanitation facilities, domestic wastewater is, after treatment, discharged to an infiltration trench at a shallow depth in the soil. Said infiltration trench generally comprises a layer of sand and / or gravel, so that the treated effluent percolates through the sand and / or gravel before infiltrating into the soil.

However, the discharge of treated effluents into such an infiltration trench generates many problems. Indeed, said infiltration trench is formed in the soil at a shallow depth so that the treated effluents 20 are discharged near the surface of the soil. It thus happens that the effluent discharge zone is quickly saturated, which may cause upsets of effluent on the surface and degrade the efficiency of the filter trench.

There is also a risk of clogging of the infiltration trench if the discharged effluent is not sufficiently treated, for example during start-up of the upstream treatment plants. It is then necessary to destroy part of the ground to remove the layer of gravel and / or clogged sand.

In addition, for a better infiltration into the ground, the length of said trench is important, which constitutes a troublesome footprint for other activities.

The object of the present invention is to propose a treatment plant which makes it possible to treat the effluent with a view to discharging it into the soil, by limiting the risks of raising the effluent on the surface, in particular for low porous soils. . In particular, another object of the invention is to provide a treatment facility for maintaining effective filtration of the effluent when an infiltration zone in the soil is saturated.

Another object of the invention is to propose a treatment plant for which the problem of clogging of the filter bed can be easily solved without having to destroy the land in which the filter bed is buried. For this purpose, the subject of the invention is an effluent treatment plant with a view to discharging said treated effluent into the soil, said installation comprising a filtration unit equipped with a filter bed, characterized in that said installation comprises a basin for receiving the filtered effluent, at least partially buried in the soil, said basin delimiting a buffer zone in which the filtered effluent can accumulate, and in that at least a part of the wall basin device has through holes made at different heights of said peripheral wall of the basin, so as to allow the discharge of the treated effluent at different depths of the ground.

Such a design of the plant according to the invention promotes a distribution of the treated effluent at different depths of the ground to take into account the hydrogeological constraints of this soil. In addition, the footprint of such a facility is reduced compared to infiltration trenches of the state of the art.

Indeed, the through orifices made at different heights in the peripheral wall of the basin allow the effluent recovered by this basin to be discharged at different heights, that is to say at different depths of the ground, which allows to evacuate the effluent in different areas of the soil in case of saturation of a part of the soil. The surface rise of the effluent, in particular through the filtration unit, is avoided, which makes it possible not to degrade the operation of said filtration unit. Indeed, the effluent can accumulate in the buffer zone and then percolate at different depths of the soil through the through holes in the peripheral wall.

When such a treatment plant is connected downstream of a sewage treatment plant, individual or collective, or an urban or industrial wastewater treatment plant, the filtration unit forms a safety filter allowing at least partly to overcome a failure of said sewage system or said treatment plant.

In particular, during a (re) start of the upstream sanitation installation 15 after a long period of inactivity, for example in the case of effluent from a secondary residence, the filtration unit makes it possible to treat the effluent, if only partially, the time that the biomass of the biological reactor is reconstituted.

Such an installation according to the invention thus promotes a good distribution of the effluent released into the soil, in a non-superficial environment. In addition, the effluent discharged to the ground is very well treated.

Finally, when the through holes are made on the circumference of the peripheral wall of the basin, the installation promotes the evacuation of the treated effluent in different orientations or directions, which improves the distribution of the treated effluent in the soil . According to an advantageous characteristic of the invention, the basin extends around the filtration unit so that said buffer zone is formed between the inner face of the peripheral wall of the basin and the outer face of the peripheral wall of the the filtration unit.

Such a design of the installation according to the invention in which the filtration unit is housed in the basin makes the installation even more compact.

According to an advantageous characteristic of the invention, said filter bed is a gravity bed, the filtration unit being configured to allow the evacuation of the effluent filtered at least in the lower part of said filtration unit, and the unit of filtration filtration rests on the bottom wall of the basin so that the buffer zone affects an annular shape, preferably circular.

Thus, the buffer zone extends around the filtration unit and on the circumference of the basin, which makes it possible to better diffuse the effluent into the soil, in particular 360 ° around the vertical axis of the basin.

According to another advantageous characteristic of the invention, the filtration unit is formed of a container, such as a tank, whose peripheral wall is preferably cylindrical, which houses said filter bed.

According to an advantageous characteristic of the invention, the peripheral wall of the container of the filtration unit has, over part of its height, through orifices made, preferably over the entire periphery of the container, at different heights of said container.

The fact of making holes or perforations at different heights of the container of the filtration unit makes it possible to improve the evacuation of the treated effluent, in particular when the buffer zone surrounds said container. Thus, the effluent continues to be filtered and then discharged into the pond, even if the orifices of the lower part of the filtration unit are flooded by the stored effluent.

Said through holes may be made in the peripheral wall of the container of the filtration unit to only a portion of the height of the filter bed. The fact of practicing the through orifices on only a part of the height of the container, and in particular only a part of the height of the filter bed, forces the effluent to pass through a given minimum thickness of the filter bed before it can be evacuated. through the through holes. According to another advantageous characteristic of the invention, the filter bed is housed in a porous envelope filled at least partially with filtering and / or adsorbent materials.

In case of clogging, the filter bed can be easily replaced by removing the porous envelope containing the filter material and / or adsorbent, without having to destroy part of the ground. The filter formed by said envelope filled with filtering material and / or adsorbents is easily replaceable. In addition, any clogging of the filter can be detected by visual inspection. Advantageously, at least the portion of the peripheral wall of the basin which has through-orifices is surrounded by a layer of gravel through which is intended to percolate the treated effluent discharged from the buffer zone of the basin, before infiltrating in the ground. According to an advantageous characteristic of the invention, the basin is furthermore equipped with an overflow outlet communicating with a discharge pipe which extends along a substantially horizontal infiltration trench practiced in the ground. and which is perforated over at least a portion of its length to distribute the overflow of recovered effluent along said infiltration trench.

Such overflow outlet allows in particular to evacuate the overflow during punctual or seasonal lift webs when deep infiltration is not possible.

The invention also relates to a treatment station comprising a treatment finishing installation formed by a treatment plant 5 as described above, characterized in that said finishing treatment plant is connected downstream of a plant of purification of domestic effluents, whether individual or collective, or of an urban or industrial wastewater treatment plant. Said purification plant or said purification plant preferably comprises a primary treatment system configured to recover and decant said effluent, and a secondary treatment system configured to degrade the effluent biologically. The treatment finishing installation according to the invention then constitutes the tertiary treatment step. The invention will be better understood on reading the following description of exemplary embodiments, with reference to the appended drawings in which: FIG. 1 is a side sectional view of the effluent treatment plant in the ground according to the invention connected to a monobloc sanitation installation; - Figure 2 is a sectional view from above of the processing plant of Figure 1; - Figure 3 is a schematic view of a removable filter cartridge which forms the filter bed of the treatment plant according to the invention; FIG. 4 is a side sectional view of the treatment plant according to the invention, connected to a sanitation installation formed of several modules.

Referring to the figures and as recalled above, the invention relates to an effluent treatment plant 1 for the discharge of said treated effluent into the soil. Said treatment plant comprises a filtration unit 3 equipped with a filter bed 5.

In the example illustrated in the figures, said treatment plant 1 is connected downstream of a sewage treatment plant 2 of domestic effluents, whether individual or collective, or of an urban or industrial wastewater treatment plant. . It should be noted that "treatment" means, throughout the text, also the purification of wastewater.

Said sanitation installation 2 comprises a primary treatment system 21 which is formed, in the example illustrated in the figures, by a first decanter 21 of the effluent to be purified. Said purification plant 2 further comprises a secondary treatment system formed of a biological reactor 22 configured to receive the effluent from the first settler 21. The secondary treatment system also comprises a second decanter 23 downstream of the biological reactor 22 The sanitizing plant 2 may also consist of separate modules providing the same functions or consist of a mini activated sludge purification station. Said installation 2 may be monoblock, as illustrated in FIG. 1, or formed of two separate modules as illustrated in FIG. 4.

The treatment plant 1 according to the invention is then used to carry out a so-called tertiary treatment of the effluent treated by the purification plant 2.

A pipe 11 connects the autonomous sanitation installation 2 to the filtration installation. The pipe 11 extends from a first end located at the level of the second decanter 23 of the purification plant 2 to an opposite second end opening above the filtration unit 3 for the purpose of filtering the water. effluent recovered. The treatment plant 1 comprises a basin 4 for receiving the filtered effluent, or filtrate, at least partially buried in the soil S. Said pond 4 delimits a buffer zone in which the filtered effluent can accumulate in particular when a portion of the soil is saturated or when the soil slowly absorbs the discharged effluent. In the example illustrated in the figures, the peripheral wall of the basin is cylindrical of circular section, but may also be of square or rectangular section. By "basin" is meant here a reservoir having a bottom wall bordered by a peripheral wall which extends substantially about a vertical axis. The peripheral wall 40 of the basin 4 has, preferably over its entire circumference, through orifices 41 at different heights of said peripheral wall 40, so as to allow the evacuation of the treated effluent at different depths of the ground. In the example illustrated in the figures, the through orifices 41 are formed in the peripheral wall 40 of the basin 4 in a regular manner around the axis of the basin. Said orifices are preferably provided on only part of the height of the basin, advantageously the lower part.

As a variant, the peripheral wall of the tank 40 may comprise orifices formed only from a certain height, if, for example, it is desired to avoid collecting water from a permanent sheet located near the peripheral wall, at a lower dimension to said orifices.

In the example illustrated in the figures, the basin 4 extends around the filtration unit 3 so that said buffer zone is formed between the inner face of the peripheral wall 40 of the basin 4 and the outer face of the peripheral wall 40 of the filtration unit 3.

In particular, the recovery basin 4 and the filtration unit 3 are sized so that the filtration unit 3 can rest in the center of the bottom wall of the basin 4 leaving free between the inner periphery of the basin 4 and the outer periphery of the filtration unit 3, an annular space forming said buffer zone in which the effluent treated at the outlet of the filtration unit can accumulate, before being evacuated by the perforations of the wall 25 peripheral of the basin.

The filtration unit 3 is formed of a vessel whose peripheral wall 30 is preferably cylindrical of circular section (or of rectangular or square section), and which houses said filter bed 5. Said filter bed 5 is a gravity bed and the filtration unit 3 is configured to allow evacuation of the filtered effluent at least in the lower part of said filtration unit. For this purpose, the peripheral wall 30 of the tank has, over part of its height, through-holes 31 made, preferably all around the circumference of the tank, at different heights of said tank. Said through holes 31 are formed in the peripheral wall 30 of the tank from the lower part of the tank, to only a portion of the height of the filter bed 5.

The diameter of the through-holes 31 made in the peripheral wall 30 of the tank is preferably between 10 and 40 mm. The diameter of the through holes 41 made at different heights of said peripheral wall 40 is preferably between 40 and 60 mm.

Preferably, as illustrated in FIG. 1, said filter bed 5 is sandwiched between two layers of gravel, respectively upper 91 and lower 92. The upper gravel layer 91 promotes the distribution of the effluent through the filter bed and the lower gravel layer 92 promotes the distribution of the filtered effluent during its evacuation through the through holes 31.

The filter bed 5 is formed of a porous envelope 52 filled at least partially with filtering and / or adsorbent materials 51 so as to form a filter "cartridge" which can be easily replaced in case of clogging of the filter bed (see FIG. Figure 2).

Provision can be made for at least a portion of the material used to form the filter bed 5 to be physically and / or chemically and / or biologically reactive with the effluent. The material used is adapted to the characteristics of the effluent to be treated. In particular, to treat an effluent whose suspended matter content (MES) is greater than a given threshold, it can be provided that the filter bed is formed of sand. In the case where the effluent to be treated has a chemical oxygen demand (COD) greater than a given threshold, activated carbon may be used to form the filter bed. Said material used to form the filter bed may further comprise aggregates such as pozzolan or PUNR (used tires 2945753 non-reusable) ground material. The filter bed can also be formed of several of these materials, divided into different layers or mixed homogeneously.

Advantageously, at least the part of the peripheral wall 40 of the basin 4s which has through holes 41 is surrounded by a layer of gravel 93 through which is intended to percolate the treated effluent discharged from the buffer zone of the basin 4, before infiltrating the soil.

The gravel layer 93 makes it possible to promote the distribution of the effluent in the soil. Said gravel layer which extends around the peripheral wall of the basin extends over the perforation height of the peripheral wall so as to form a transition zone for evacuation of the effluent before it infiltrates. in the ground. The presence of such an envelope of gravel 93 also prevents the through holes in the peripheral wall of the basin from being clogged by the ground soil.

As illustrated in FIG. 1, the basin 4 is furthermore equipped with an overflow outlet communicating with a discharge pipe 6 situated above the through orifices 41 formed in the peripheral wall 40 of said basin. that is to say in the upper part of the basin. The evacuation pipe 6 extends along a substantially horizontal infiltration trench 94 made in the ground. Said evacuation pipe 6 is perforated over at least a part of its length in order to distribute the overflow of recovered effluent along said infiltration trench 94. It can also be provided to have a pumping column 7 associated with a pumping system to collect the treated effluent accumulated after filtration in the buffer zone. The treated effluent recovered via the pumping column 7 may be used for example for watering. It may also be provided to apply a UV treatment or other antibacterial treatment to the treated effluent recovered by pumping so as to destroy any bacteria still present in said effluent.

Advantageously, a sampling column 8 extends substantially vertically through the filtration bed of the filtration unit so as to be able to take effluent samples at different heights of the filter bed. The column or sampling well is formed by a hollow tube perforated laterally so as to collect a portion of the filtered effluent at different depths of the filter bed, to check for example the degree of clogging of the filter bed.

Advantageously, the head 11A of the pipe 11 connecting the sanitation installation 2 to the treatment plant 1, which opens in the upper part of the filtration unit 3 is removable so as to easily remove the "cartridge forming the filter bed 5.

As illustrated in FIG. 1, the basin buried in the ground comprises a cover 42 of the gaze type which is flush with the surface of the ground so as to allow easy direct access to the filtration unit, in particular so that, if necessary, it can be extracted. "cartridge" forming a filter bed 5.

The treatment plant 1 according to the invention can operate without energy input (apart from optional pumping, for example for watering) and is thus suitable as a tertiary treatment plant for individual sewerage units of which it constitutes a advantageous complement. The volume of the buffer zone is sized according to the intended use of the treatment facility and may, for example, be approximately six days of operation, for a family of about six people, from the primary and secondary installation to the facility. which the treatment plant according to the present invention is connected.

Alternatively, it could also be provided that the treatment plant 1 30 according to the invention operates autonomously without upstream pretreatment, depending on the quality of the effluent input. The present invention is not limited to the embodiments described and shown, but the skilled person will be able to make any variant within his mind.

Claims (10)

REVENDICATIONS1. An effluent treatment plant (1) for discharging said treated effluent into the soil, said plant comprising a filtration unit (3) equipped with a filter bed (5), characterized in that said installation ( 1) comprises a basin (4) for receiving the filtered effluent, at least partially buried in the soil, said basin (4) delimiting a buffer zone in which the filtered effluent can accumulate, 10 and in that at least a portion of the peripheral wall (40) of the basin (4) has through orifices (41) formed at different heights of said peripheral wall (40) of the basin, so as to allow the evacuation of the effluent treated at different depths of the ground. 15 2. Treatment plant (1) according to claim 1, characterized in that the basin extends around the filtration unit such that said buffer zone is formed between the inner face of the peripheral wall (40) of the basin (4) and the outer face of the peripheral wall (40) of the filtration unit (3). 20 3. Treatment plant (1) according to one of the preceding claims, characterized in that said filter bed (5) is a gravity bed, the filtration unit (3) being configured to allow the evacuation of the effluent filtered at least in the lower part of said filtration unit, and in that the filtration unit (3) rests on the bottom wall of the basin (4) so that the buffer zone has an annular shape, preferably circular . 4. Treatment plant (1) according to one of the preceding claims, characterized in that the filtration unit (3) is formed of a container, such as a tank, whose peripheral wall is preferably cylindrical which houses said filter bed (5). 13 5. Treatment plant (1) according to claim 4, characterized in that the peripheral wall (30) of the container of the filtration unit has, over part of its height, through orifices (31) made, preferably on the entire periphery of the container, at different heights of said container. 6. Treatment plant (1) according to claim 5, characterized in that said through holes (31) are formed in the peripheral wall (30) of the container of the filtration unit to only a portion of the height of the filter bed (5). 7. Treatment plant (1) according to one of the preceding claims, characterized in that the filter bed (5) is housed in a porous envelope (52) at least partially filled with filtering materials (51) and / or adsorbents. 15 8. Treatment plant (1) according to one of the preceding claims, characterized in that at least the portion of the peripheral wall (40) of the basin (4) which has through holes (41) is surrounded by a gravel layer (93) through which is percolated the treated effluent discharged from the basin buffer zone (4), before infiltrating the soil. 9. Treatment plant (1) according to one of the preceding claims, characterized in that the basin (4) is furthermore equipped with an overflow outlet communicating with a discharge pipe (6) extending along a substantially horizontal infiltration trench (94) made in the ground and perforated over at least part of its length to distribute the overflow of recovered effluent along said infiltration trench ( 94). Processing station comprising a finishing treatment plant 30 formed by a treatment plant (1) according to one of the preceding claims, characterized in that said finishing treatment plant is connected downstream of a treatment plant. sanitation (2) of domestic effluents, individual or collective, or a wastewater treatment plant 10 urban or industrial wastewater, said sanitation plant (2) or purification plant preferably comprising: - a primary treatment system (21) configured to recover and decant said effluent; - a secondary treatment system (22) configured to biologically degrade the effluent.